001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.collections4;
018
019import java.util.ArrayList;
020import java.util.EmptyStackException;
021
022/**
023 * An implementation of the {@link java.util.Stack} API that is based on an
024 * <code>ArrayList</code> instead of a <code>Vector</code>, so it is not
025 * synchronized to protect against multi-threaded access.  The implementation
026 * is therefore operates faster in environments where you do not need to
027 * worry about multiple thread contention.
028 * <p>
029 * The removal order of an <code>ArrayStack</code> is based on insertion
030 * order: The most recently added element is removed first.  The iteration
031 * order is <i>not</i> the same as the removal order.  The iterator returns
032 * elements from the bottom up.
033 * </p>
034 * <p>
035 * Unlike <code>Stack</code>, <code>ArrayStack</code> accepts null entries.
036 * <p>
037 * <b>Note:</b> From version 4.0 onwards, this class does not implement the
038 * removed {@code Buffer} interface anymore.
039 * </p>
040 *
041 * @param <E> the type of elements in this list
042 * @see java.util.Stack
043 * @since 1.0
044 * @deprecated use {@link java.util.ArrayDeque} instead (available from Java 1.6)
045 */
046@Deprecated
047public class ArrayStack<E> extends ArrayList<E> {
048
049    /** Ensure serialization compatibility */
050    private static final long serialVersionUID = 2130079159931574599L;
051
052    /**
053     * Constructs a new empty <code>ArrayStack</code>. The initial size
054     * is controlled by <code>ArrayList</code> and is currently 10.
055     */
056    public ArrayStack() {
057        super();
058    }
059
060    /**
061     * Constructs a new empty <code>ArrayStack</code> with an initial size.
062     *
063     * @param initialSize  the initial size to use
064     * @throws IllegalArgumentException  if the specified initial size
065     *  is negative
066     */
067    public ArrayStack(final int initialSize) {
068        super(initialSize);
069    }
070
071    /**
072     * Return <code>true</code> if this stack is currently empty.
073     * <p>
074     * This method exists for compatibility with <code>java.util.Stack</code>.
075     * New users of this class should use <code>isEmpty</code> instead.
076     *
077     * @return true if the stack is currently empty
078     */
079    public boolean empty() {
080        return isEmpty();
081    }
082
083    /**
084     * Returns the top item off of this stack without removing it.
085     *
086     * @return the top item on the stack
087     * @throws EmptyStackException  if the stack is empty
088     */
089    public E peek() throws EmptyStackException {
090        final int n = size();
091        if (n <= 0) {
092            throw new EmptyStackException();
093        }
094        return get(n - 1);
095    }
096
097    /**
098     * Returns the n'th item down (zero-relative) from the top of this
099     * stack without removing it.
100     *
101     * @param n  the number of items down to go
102     * @return the n'th item on the stack, zero relative
103     * @throws EmptyStackException  if there are not enough items on the
104     *  stack to satisfy this request
105     */
106    public E peek(final int n) throws EmptyStackException {
107        final int m = (size() - n) - 1;
108        if (m < 0) {
109            throw new EmptyStackException();
110        }
111        return get(m);
112    }
113
114    /**
115     * Pops the top item off of this stack and return it.
116     *
117     * @return the top item on the stack
118     * @throws EmptyStackException  if the stack is empty
119     */
120    public E pop() throws EmptyStackException {
121        final int n = size();
122        if (n <= 0) {
123            throw new EmptyStackException();
124        }
125        return remove(n - 1);
126    }
127
128    /**
129     * Pushes a new item onto the top of this stack. The pushed item is also
130     * returned. This is equivalent to calling <code>add</code>.
131     *
132     * @param item  the item to be added
133     * @return the item just pushed
134     */
135    public E push(final E item) {
136        add(item);
137        return item;
138    }
139
140    /**
141     * Returns the one-based position of the distance from the top that the
142     * specified object exists on this stack, where the top-most element is
143     * considered to be at distance <code>1</code>.  If the object is not
144     * present on the stack, return <code>-1</code> instead.  The
145     * <code>equals()</code> method is used to compare to the items
146     * in this stack.
147     *
148     * @param object  the object to be searched for
149     * @return the 1-based depth into the stack of the object, or -1 if not found
150     */
151    public int search(final Object object) {
152        int i = size() - 1;        // Current index
153        int n = 1;                 // Current distance
154        while (i >= 0) {
155            final Object current = get(i);
156            if ((object == null && current == null) ||
157                (object != null && object.equals(current))) {
158                return n;
159            }
160            i--;
161            n++;
162        }
163        return -1;
164    }
165
166}